1. Field of the Invention
The present invention relates to a reclining adjuster which is attached to a seat for a vehicle and the like to appropriately adjust an inclination angle of a seat back to a seat cushion, and, in particular, to a technology to realize reduction of play of the seat back at the time of locking and so on.
2. Description of the Related Art
In a reclining adjuster disclosed in Japanese Utility Model Publication No. Sho 42-7950, a sector gear (a worm wheel) is fixed to a seat back, while a worm which is fittable with the sector gear is pivotably attached to a seat cushion.
The worm is connected to an operation shaft and engagement of the worm with the sector gear is released by drawing the operation shaft along the axial direction thereof and lifting it up further.
When a load is added to the seat back in this state, the seat back inclines so that the inclination angle can be promptly changed, and when the hand is off from the operation shaft, the worm engages with the sector gear again to hold the seat back at its position.
When a slight adjustment of the inclination angle of the seat back is required, the operation shaft is pivoted to allow the worm to rotate, which makes the sector gear engaging with the worm rotate gradually, so that the seat back can be changed to an arbitrary inclination angle steplessly.
In recent years, as is disclosed in Japanese Patent Laid-open Publication No. Hei 10-217817, a reclining adjuster is proposed, in which a worm having a lead angle equal to or more than the angle of friction and a sector gear are attached to the seat cushion and the seat back respectively, and by inclining the seat back, the worm is allowed to rotate through the sector gear so that the inclination angle of the seat back is appropriately changed.
However, in a case of a reclining adjuster having a sector gear and a worm engaging with each other, a backlash between tooth faces of the sector gear and the worm becomes a factor of the play at the time of locking of the seat back and causes problems of generating an abnormal noise or deterioration in a feeling of seating.
When a shaft of the worm is supported rotatably with bearings such as an ordinary ball bearing and the like, clearance is provided in the thrust direction to ensure a smooth movement of the worm. This clearance also causes play at the time of locking of the seat back and becomes a factor of generating an abnormal noise or deterioration in a feeling of seating.
In Japanese Patent Laid-open Publication No. 2000-342371, disclosed is a technology to attempt to reduce a backlash by pressing a sector gear engaging with a worm in the direction along the worm with a press member. However, in order to press the sector gear supported rotatably in the radial direction (in the direction toward the worm), it is necessary to provide an arc-shaped hole on the sector gear, and it is also required to form a hole corresponding to the bracket supporting the worm or to provide a roller member to press inside walls of these holes, which makes the structure complicated and unsuitable for mass production. The backlash at the time of locking of the seat back is surely reduced and the play of the seat back can be suppressed by pressing the sector gear against the worm. However, since the clearance in the thrust direction of the worm cannot be reduced, a problem of the play at the time of locking of the seat back due to such a clearance still remains.
The present invention is performed to solve the above-described disadvantages and aims to provide a reclining adjuster which has a simple structure suitable for mass production, reduces not only a backlash, but also clearance in the thrust direction of a worm at the time of locking of a seat back so that generation of an abnormal noise is prevented and a feeling of seating is further improved.
In order to achieve the above-described objects, the reclining adjuster of the present invention comprises: a worm pivotably attached to a seat cushion; a worm wheel fixed to the seat back and engaging with the worm; and a locking mechanism selectively operated to lock the worm so as to be unable to rotate or to release the locking,
wherein recess portions are respectively provided on both end faces of the worm and on the inside end faces of a pair of support members to support the both end portions of the worm, and balls are rotatably housed respectively in a pair of spaces formed between the recesses where both end faces of the worm face a pair of the support members so that a pair of bearings are formed to rotatably support the worm, and wherein the locking mechanism includes a press means to press a tooth portion of the worm into a tooth portion of the worm wheel at the time of locking.
The above-described each recess is preferably formed substantially in a cone shape having a tapered surface on the inside face.
It is preferable that the above-described locking mechanism comprises an engaging claw which can engage and disengage with or from an engaging groove formed on a part of the tooth portion of the worm at the end portion thereof, and an arm member pivotably supported with a shaft member in order to engage and disengage the engaging claw with or from the engaging groove, wherein said press means is connected to the arm member, and is composed of an elastic member enforcing in the direction to engage the engaging claw to the engaging groove.
It is preferable that the above-described arm member is formed substantially in a shape of the letter T having a longer piece and a shorter piece, the boundary of the longer piece and the shorter piece is supported with the shaft member, the longer piece serves as an operation part, and the engaging claw is formed at a side end portion of the shorter piece. The above-described elastic member is provided between the arm member and an arbitrary fixing portion and is composed of a spring enforcing in the direction that the engaging claw engages with the engaging groove.
In this case, it is preferable that the above-described spring is provided between the other side end portion of the shorter piece of the arm member and a bracket which supports the worm.